1. Field of the Invention
This invention relates to upgrading a hydrogenated oil. More particularly, a combination process is provided wherein the nitrogen compounds of an oil, such as a coal oil, are substantially removed by a combination of coking and liquid-liquid selective extraction steps.
2. Prior Art
As a consequence of the diminishing supplies of petroleum and the corollary increase in cost thereof, extensive research efforts have been directed to develop feasible commercial processes for the production of liquid and gaseous fuels from coal resources. Of particular importance are those processes being developed for the direct conversion of coal to liquid hydrocarbon fuels or synthetic crudes. In this type of process, raw coal is typically dissolved in a hydrogen-donor solvent, or the equivalent, to produce a liquid hydrocarbon which may be further processed to produce gasoline, fuel oils, or petrochemicals. Unfortunately, the raw coal normally contains appreciable quantities of nitrogen-bearing compounds which remain in the synthetic crude. Typical levels of nitrogen compounds remaining in the coal-derived oil are usually in the range of 300 to 1000 ppmw, measured as nitrogen. It is well known in the art that nitrogen contaminants in these concentrations have a deleterious effect on most acidic catalysts used in conventional hydroprocessing steps. Under the process conditions such as those encountered in hydrotreating or hydrofining processes, the nitrogen is converted to ammonia, which acts to poison the catalyst, and causes costly shutdowns, catalyst loss, and/or expensive onstream regenerating equipment.
It is therefore an object of this invention to provide a noncatalytic process for upgrading hydrogenated oils, and particularly coal-derived oils, by substantially reducing the nitrogen contaminant content thereof.